Each configured MCP server now registers as its own toolset in TOOLSETS
(e.g. TOOLSETS['github'] = {tools: ['mcp_github_list_files', ...]}),
making raw server names resolvable in platform_toolsets overrides.
Previously MCP tools were only injected into hermes-* umbrella toolsets,
so gateway sessions using raw toolset names like ['terminal', 'github']
in platform_toolsets couldn't resolve MCP tools.
Skips server names that collide with built-in toolsets. Also handles
idempotent reloads (syncs toolsets even when no new servers connect).
Inspired by PR #1876 by @kshitijk4poor.
Adds 2 tests (standalone toolset creation + built-in collision guard).